Apparatus and a method for heating plastic preforms with a removable movement device

ABSTRACT

An apparatus for heating plastic preforms includes a first transport device that transports the plastic preforms in a separated manner, wherein said first transport device has a plurality of recesses for receiving the plastic preforms, and a second transport device that takes over the plastic preforms transported by the first transport device and transports the plastic preforms along a predetermined transport path. The apparatus has at least one sensor device that detects at least one measured value that is characteristic of at least one of the two drive devices, and a control device that is designed to control the drive device for moving the holding elements as a function of this characteristic measured value.

The present invention relates to an apparatus and a method for heatingplastic preforms. Such apparatus and methods have been known from theprior art for a long time. In these apparatus, plastic preforms producedare usually heated in an oven and are subsequently supplied in thisheated condition to a stretch blow machine that expands these plasticpreforms into plastic containers such as in particular plastic bottles.

In the course of this, the plastic preforms are fed in these heatingdevices to a heating section via a distribution star wheel such as forexample a sawtooth star wheel. In the course of this, the sawtooth starwheel separates the plastic preforms to set a predetermined pitchbetween them. Subsequently, these plastic preforms are placed on heatingmandrels. These heating mandrels are in turn moved through the heatingtunnel by means of a transport chain. The location at which the plasticpreform is transferred to the heating mandrel by the sawtooth starwheel, which will be referred to below as the transfer point for theoven infeed, must be adjusted very accurately in order to ensure aproblem-free passage of the plastic preforms.

In the case of systems known from the prior art, this sawtooth starwheel is driven via a toothed belt, which toothed belt is in turncoupled with a drive of the transport chain for the heating mandrels.The transfer point is established here once at the factory. In the priorart, if the mouth of the plastic preform is changed, then the pocketsize and thus also the transfer point will be accurately adapted via asecond sawtooth module. A displacement of this point in the case of aformat changeover is consequently possible only by changing theindividual module, i.e. the sawtooth star wheel, and only by way of amechanical post-adjustment or adjustment of the transfer point. However,the latter is not to be recommended for the operator, because this meansa time-consuming and error-prone activity.

The coupling between these drives further has the disadvantage that inthe case of jamming of the plastic preforms even a “slight” distortionof the clamping sets in the drive train will be detected either not atall or only late. As a result, the transfers of the plastic preforms(possibly also as a result of a displacement of the transfer point)deteriorate and the wear and tear of parts on the heating mandrels andtransport spindles will increase unnoticed.

Further, if the mouths of the plastic preforms in the neck diameter arelocated very close to each other, then these will be moved with one andthe same sawtooth star wheel. Thus, part costs will be saved, and aboveall, the unpopular changes and changeover times at the customer's willbe avoided.

The gradation of the diameter change of the plastic preform isapproximately 1 mm. As a consequence, the transfer point can, in theworst case, may be displaced by 0.5 mm or, as a result, deteriorate.

In these cases, at least one transfer point will not or never be ideallyadjusted. Either one transfer point is adjusted ideally and the otherone consequently badly, or none of the two transfer points is adjustedbadly but not ideally either.

Although this approach is advantageous in so far as the operator doesnot need to change the modules, however it has the disadvantage that thetransfer accuracy at the oven infeed suffers. As a result, placementerrors may more frequently occur, which in turn reduces the transferquality in general and also to the subsequent machine module.

Also, the wear and tear of the preforms increases as a result of anon-central plunging of the holding mandrel into the plastic preform,which can be detected by an increased PET abrasion in the machine.

The present invention is therefore based on the object of proposing anapproach that avoids such inaccuracies during transfer. In other words,a possibility is supposed to be provided in order to select ideallyalways the best-possible transfer point for the plastic preforms. Afurther object of the invention consists in preventing damage to themachine in the case of inaccuracies occurring.

According to the invention, this object is achieved by the subjectmatter of the independent claims. Advantageous embodiments anddevelopments are the subject matter of the dependent claims.

An apparatus according to the invention for heating plastic preforms hasa first transport device that transports the plastic preforms in aseparated manner, wherein this first transport device has a plurality ofreception means for receiving the plastic preforms. Further, theapparatus comprises a second transport device that takes over thetransported plastic preforms from the first transport device andtransports these plastic preforms along a predefined transport path.

Further, the second transport device comprises a plurality of holdingelements for holding the plastic preforms, and further, at least oneheating device is provided that heats the plastic preforms transportedby the second transport device. In the course of this, at least thefirst transport device is a circulating transport device.

According to the invention, the relative position of the reception meansof the first transport device in the circumferential direction of thefirst transport device can be modified in relation to a position of theholding elements with regard to the transport path.

This approach allows faults to be prevented, in order to ensure in thisway in particular correct transfer points. Thus, this approach allowsthe risk of damage to the machine to be reduced.

Instead of or in addition to the change of the transfer position asdescribed here, it would however also be possible to prevent damage inthe case of occurring errors in the transfer position by means of asafety device.

The invention is therefore also directed to a machine of the typedescribed above, which moreover has a further drive device for movingthe holding elements in a longitudinal direction of the plasticpreforms, wherein the apparatus additionally includes at least onefurther drive device for driving at least one transport device.

According to the invention, the apparatus has at least one sensor devicethat detects at least one measured value that is characteristic of atleast one of the two drive devices, and a control device that issuitable and designed for controlling the drive device for moving theholding elements as a function of this characteristic measured value.Preferably, this control device is a closed-loop control device thatcontrols the drive device. An input variable of this control device isthus preferably the measured value detected by the sensor device, forexample a measured value that is characteristic of a torque of a drivedevice.

In this approach it is proposed, as will be explained in more detailbelow, to detect by means of said measured value whether faults areoccurring or will occur, and in this case, the movement of the holdingelements is for example stopped, so that a transfer of the plasticpreforms from the first transport device to the second transport devicewill not occur. This sensor device may optionally also be present in thecase of the embodiment described above.

A movement of the holding elements in the longitudinal direction of theplastic preforms is in particular understood to mean that the lattermove exactly along the longitudinal direction. However, a movement in adirection obliquely thereto would also be conceivable.

Thus, in particular the second transport device is disposed downstreamof the first transport device in the transport direction of the plasticpreforms. Preferably, the second transport device follows directly fromthe first transport device and/or takes over the plastic preformsimmediately from the first transport device. Preferably, the secondtransport device also transports the plastic preforms in a separatedmanner. Preferably, a pitch of the reception means of the firsttransport device corresponds to a pitch of the holding devices of thesecond transport device.

Thus, it is proposed in the first approach illustrated above that an inparticular targeted change to the circulation position of the receptionmeans relative to the circulating position of the holding means can becarried out, in particular in order to ensure that the transfer point,at which the plastic preforms can be taken over by the holding elementsproceeding from the reception means, can be, adapted or modified. Withthe second approach, further errors that may develop in particular as aresult of an unwanted displacement of the transfer point can be avoided.

As mentioned above, a common drive is provided in the prior art, so thatthe two transport devices are coupled. No fine correction is provided.It is now proposed within the scope of the invention to design thiscoupling so that it can be separated at least at times, so that thetransfer point can be adjusted.

A circulating transport means is understood to mean that the receptionmeans move here along a closed movement path, in particular a circularmovement path and/or a movement path with curved sections.

In a further preferred embodiment, the first transport device has arotatable carrier and the reception means are preferably recesses thatare provided in particular on an outer circumference of this carrier.These recesses are also referred to as “pockets”. These reception meansare used for receiving sections of the plastic preforms, in particularsections that are located below a carrying ring of the plastic preforms.Preferably, the first transport device also includes a guiding elementsuch as in particular a guiding rail that extends around the rotatablecarrier. The plastic preforms are preferably guided between this guidingrail and the reception means.

In a further advantageous embodiment, the heating devices are mounted tobe stationary relative to the transport path of the plastic preforms. Inparticular, these are heating devices that apply infrared radiation ontothe plastic preforms. Preferably, the heating devices have heating tubesor radiant heaters that preferably extend, at least in sections, alongthe transport path of the plastic preforms. However, it would also bepossible for the heating device to be a microwave heating device thatapplies microwaves onto the plastic preforms for the heating thereof.Also, individual microwave stations may be provided here that areconveyed on a movable, for example a rotatable, carrier.

The holding elements of the second transport device are preferablymandrels that can be introduced into the mouths of the plastic preforms.These mandrels preferably have the same pitch as the reception means ofthe first transport device.

In a further advantageous embodiment, the device has a further drivedevice for moving the holding elements or mandrels in the longitudinaldirection of the plastic preforms. This drive device may for example bea guiding or actuating cam that effects, due to the transport movementsof the holding elements, also a movement of the holding elements in thelongitudinal direction of the plastic preforms.

Further, the apparatus preferably has a rotation device that rotates theholding elements about the longitudinal direction thereof and rotates inparticular, at least at times, during the heating. This also allows aneven heating of the plastic preforms in the circumferential directionthereof.

As mentioned, the reception means of the first transport device arepreferably pockets or recesses that receive the plastic preforms.Advantageously, the second transport device is also designed tocirculate (and transports for example the plastic preforms along atransport path that is composed of rectilinear and curved sections).Particularly preferably, the second transport device has a transportchain, on which the holding elements are provided. Preferably therefore,as mentioned above, the first transport device and the second transportdevice are decoupled from each other with regard to their transportmovements and/or can be decoupled at least at times.

In a further preferred embodiment, the first transport device has afirst drive device for driving the first transport device, and thesecond transport device has a second drive device for driving the secondtransport device. Thus, unlike the prior art, different or from eachother separated drive devices are proposed. In particular, these drivedevices are not coupled together here. Preferably, at least one of thesedrive devices and in particular both drive devices are electromotoricdrive devices and in particular servo motors. Servo motors offer theadvantage that they allow polling of certain measured values, forexample torques, in a relatively uncomplicated manner.

In a further advantageous embodiment, the first drive device and thesecond drive device can be controlled independently of each other. As aresult of this independent controllability, the transfer point or theposition of the transfer point can be adjusted and/or changed. Inparticular, the transfer point can be corrected as a result of this.

For the correction, in particular an offset correction between the twodrive devices, several approaches are conceivable. It would thus beconceivable that the operator of the machine him/herself establishes thecorrection parameters. Thus, the correction parameter for anotherplastic preform could be input via an input means (such as for example akeypad or a touch screen). The device can then automatically adjust theoffset between the two drives to the changed parameter. It would also beconceivable for the operator himself to adjust the offset.

It would further be conceivable for the operator only to select therespective recipe deposited in the machine. Correction parameters arepreferably already deposited in the type parameters of the machine orare calculated by the machine using certain parameters. In this contextit would be conceivable to deposit in the already depositedpreform-bottle recipes (=type parameters) of the machine control alsofurther parameters, such as for example the respective preform neckparameter L1 (i.e. the diameter in the region in which the plasticpreform is grasped by the first reception device). In the case of aformat changeover, the operator must re-select or load a depositedrecipe. It thus continues to be possible to install (for example betweenthe machine control and the servo control of the drive device) aprocessor device that determines the difference angle from both preformsizes. This difference angle can be forwarded to the servo axis as thecorrection angle (e.g. as in FIG. 5, 0.154°). Preferably, the machinecan adjust itself to the new format in relation to the oven infeed.Thus, a fully automatic change of the transfer points may be carriedout.

In this context it is possible for a control matched to the two drivedevices to be present.

Moreover, also a sensor device may be provided, in order to carry out anautomatic correction of the transfer point. Thus, for example, a sensordevice can detect a diameter of the plastic preform and can control oreffect a corresponding offset of the two transport devices relative toeach other as a function of a changed diameter (or can adapt thetransfer point).

By driving the second transport device or the transport chain anddriving the first transport device or the sawtooth star wheel using aseparate drive for each, for example a servo drive, it is possible tocompensate in such cases a displacement of the transfer point. All theoperator needs to do is to input the correction parameter for examplefor a second variable (the mouth diameter) of a second plasticpreform—in particular on a control panel of the machine—and the machinecan adjust itself to the respectively optimal transfer points. In thisway, an actual change of module, which would be substantially more timeconsuming, can be avoided. However, it would—as mentioned above—also bepossible, in particular by using sensor devices, to cause such achangeover to be carried out automatically (i.e. without the involvementof the user).

By means of the proposed approach, a plurality of disadvantages of theprior art can thus be remedied. Thus, it can be prevented that in thecase of a displacement of the transfer point, the wear and tear of partson the heating mandrels and the transport spindles increases unnoticedor that preforms jam, which could consequently lead to a lack ofsynchronicity between the transport chain and the sawtooth star wheel,which could also cause serious damage to the machine as a whole. Damageoccurs above all if the holding elements were plunged into the preformdespite a lack of synchronicity. In order to avoid plunging in the caseof a lack of synchronicity, a protection device, such as for example inthe form of a controllable lifting cam, must be provided for in thedesign.

In a further advantageous embodiment, the drive device that is used formoving the holding elements in the longitudinal direction of the plasticpreforms, can be deactivated and can in particular be deactivated duringthe on-going operation. Thus, it is in particular possible that thedrive device is deactivated during the continued operation of the deviceand in particular during the continued operation of the first transportdevice. The applicant reserves the right to claim this aspect alsoindependently of the above-described invention, i.e. irrespective ofwhether a decoupling of the two transport devices should be possible.

In a further advantageous embodiment, the device includes a controllablelifting cam that is used for feeding the holding mandrels into themouths of the plastic preforms. In this case, this lifting cam is theabove-mentioned drive device. This lifting can if required be switchedoff, so that the holding elements are not fed into the plastic preforms.This means at the same time a deactivation of the drive device.

Since the actual problem in the case of preform jamming is thenon-detection of a displacement of the transfer point, i.e. the transferof the plastic preform, the separate servo drive offers the possibilityof detecting excessive or high torque increases. Such increases of thetorques are usually precursors of jams, so that a corresponding signalcan be transmitted to the machine control, so that the cam liftingsegment is switched off at an early stage during the transfer of theplastic preform. As a result, no engagement of the holding mandrel or ofthe holding element in the plastic preform takes place. This may inparticular take place in case a subsequent lack of synchronicity islikely to occur.

Preferably, the apparatus therefore has a sensor device that detects inparticular characteristic values that are characteristic of anyoccurring or imminent errors during the operation of the device. Thismay, as mentioned, for example be a torque measurement device thatdetects torques of the drive device of the transport device and/orvariables that are characteristic of such a torque or that resulttherefrom, such as electric currents. In other words, the sensor devicepreferably detects at least one measurement value that is characteristicof a torque of the at least one drive device (which drives the at leastone transport device). This measured value may for example be a currentthat is used to drive this drive device.

This measured value is preferably detected continuously over apredetermined period of time. It is possible here for this measuredvalue to be compared with a reference value. In case this measurementvalue exceeds the reference value, then this can be evaluated to be anindication that the torque is also too high. In this case, the guidingcam can for example be switched off, so that no further plastic preformsare transferred.

Preferably, the drive device has a guiding cam for moving the holdingelement, which extends preferably at least in sections along thetransport path of the plastic preforms. The guiding cam preferablyeffects here the feeding of the holding elements towards the plasticpreforms. This guiding cam can here preferably be switched, i.e. can bemoved for example from a working position, in which it causes theholding elements to be fed towards the plastic preforms, into a restingposition, in which the holding elements are not fed.

Preferably, for moving the holding element, the drive device thereforehas an actuating device for moving the guiding cam. This actuatingdevice may for example be an electromotoric drive. Apart from that,however, also the use of hydraulic or pneumatic drives would beconceivable.

In such situations, as described above, it would also be possible tocarry out a correction of the transfer point. If a servo drive or aservo axis is provided, it is possible to record or evaluate thecurrently necessary torque. The operating moment necessary in the caseof properly loaded plastic preforms is known. If the torque rises beyonda predefined limit (e.g. three times the operating torque), theswitchable lifting cam segments of an oven infeed are switched off as amatter of precaution.

In a further advantageous embodiment, the device therefore has a sensordevice that detects at least one value that is characteristic of thetransfer of the plastic preforms from the first transport device to thesecond transport device. Advantageously this is a torque that isrequired for example in order to feed a holding element of the secondtransport device towards the plastic preforms. The servo axis or thedrive, which is capable of handling a multiple of the drive torque,continues to rotate synchronously. If the torque does not continue torise, the machine continues to run in the production operation, howeverwithout loading the defective plastic preforms. It is then not possibleeither for these plastic preforms to cause damage or attachment errorsat the oven infeed and at subsequent plastic bottle transfers orgenerally in processing steps.

However, if the torque continues to rise, then this is an indicationthat there will be a preform jam and consequently a lack ofsynchronicity. In this case, the servo drive can advantageously alsofunction as an electric coupling and can be switched off or disengaged.In this case, a machine control will preferably issue the signal for acontrolled stop of the machine and the operator can remove the one ormore defective plastic preforms from the sawtooth.

In both cases, the machine components are protected from the detrimentalconsequences of plastic preform jams or of poorly fed plastic preforms.

In a further advantageous embodiment, a control device is provided thatcan adjust or correct an offset between the positions of the firsttransport device and the position of the second transport device (and inparticular between the reception means of the first transport device andthe holding elements of the second transport device). Advantageously,the drive devices each have, as mentioned above, servo drives.

However, independently of the drive solution described here, also amechanical solution would be conceivable. It would therefore beconceivable for an offset of the sawtooth star wheel or a modificationto the rotary position relative to the drive to be carried out manually.It would thus further be possible for the drive of the first and secondtransport devices to be coupled to each other, so that in principle apermanent coupling is achieved. However, this coupling could be releasedby user intervention, for example by allowing a certain change to therotary position of the first transport device or of a rotatable sawtoothstar wheel relative to its carrier, for example a shaft, to be carriedout.

In this case, the user could, for example when changing over to slightlydifferent plastic preforms, also modify the relative rotational positionof the first transport device or of the sawtooth star wheel relative tothe second transport device, in particular the transport chain. It wouldthus be possible for the first transport device to have a rotatableshaft and for a sawtooth star wheel to be provided on this shaft. Therotary position of this sawtooth star wheel relative to the shaft can inparticular be changed by user intervention.

It would be possible here that as a result of this change to therotational position, a certain bandwidth of a plastic preform can beprocessed. For example, the user could obtain information via tables asto the rotational position the sawtooth has to be taken to for an idealadjustment of the transfer point. In so far, also a semi-automaticadjustment would be possible. Thus, a sensor device could detect forexample a misorientation, or an angle to which the sawtooth has to berotated so as to ensure an ideal transfer point could be communicated tothe user. Thus, for example, the first transport device could alsoinclude a reading device such as a scale that indicates the exactangular position of the sawtooth star wheel to the user. Apart fromthat, however, it would also be conceivable to provide a drive foradjusting such an offset.

In a further advantageous embodiment, the apparatus has a supply devicein order to supply the plastic preforms to the first transport device.Preferably, the first transport device separates these plastic preformsfrom each other. As such a supply device, for example a supply rail maybe provided, in which the plastic preforms are transported in particularso as to directly follow each other.

In a further advantageous embodiment, the apparatus has a control devicefor controlling the two drive devices. Thus, a higher-level control ispreferably provided here, which controls both drive devices and inparticular controls them in such a way that a transfer point can beideally adjusted. Preferably, the control device is a closed-loopcontrol device that is capable of adjusting the transfer point. As anactuation variable for such a control device, for example theabove-mentioned torque, and as a control variable, the offset betweenthe transport devices could be used here.

Advantageously, this control device is suitable and designed to controlat least one of the two drive devices also on the basis of a parameterthat is characteristic of a geometry of the plastic preforms. Inparticular, one or both drive devices can here also be controlled as afunction of the neck diameter of the plastic preforms. This neckdiameter results, as will be explained in more detail below, ifnecessary in a displacement of the transfer point. The control devicecan here control or adjust, for example on the basis of a user input forexample on the basis of a new recipe, an offset between the twotransport devices, so that again an ideal transfer point for the plasticpreforms is achieved.

In a further advantageous embodiment, the device has a processor devicethat determines and/or calculates an offset between both drive deviceson the basis of at least one characteristic variable of a plasticpreform. This characteristic variable is in particular a neck geometry,i.e. in particular a comparison of the two neck geometries. From thiscomparison, a correction angle can be determined.

In a further advantageous embodiment, a relative position of thereception means of the first transport device in the circulationdirection of the first transport device is or can be modified relativeto a position of the holding element with respect to the transport path,in order to modify in this way the take-over position or the transferpoint, on which the second transport device takes over the plasticpreforms. Advantageously here, a slight modification is possible,particularly preferably a modification of +/−5° in relation to thecirculation length (i.e. the circulation travel of a reception means),preferably of +/−3%, preferably of +/−1%, preferably of +/−0.5% andpreferably of +/−0.3%.

As mentioned above, the first transport device preferably has arotatable carrier and the reception means are preferably formed asrecesses on an outer circumference of this carrier. This carrier isadvantageously exchangeable or can be replaced with another carrier.Thus, for example carriers having different geometries of the receptionpockets may be replaced with each other.

The present invention is further directed to a method for heatingplastic preforms, and the plastic preforms can be transported by meansof a first transport device by means of reception means of the firsttransport device and can be taken over by a second transport device at apredetermined transfer position and can be transported by this secondtransport device using holding elements that hold the plastic preformsalong a predetermined transport path. Further, the plastic preforms are,at least temporally during this transport along the transport path,heated by at least one heating device.

According to the invention, a relative position of reception means ofthe first transport device in the circulation direction of the firsttransport device relative to a position of the holding elements inrelation to the transport path (the holding element) can be changed. Inother words, this relative position is preferably changed in a targetedmanner, for example in order to change a change-over operation, inparticular as a function of geometric parameters of the plasticpreforms. Preferably, the change to the relative position is carried outin order to change a transfer point at which the plastic preforms aretransferred from the first transport device to the second transportdevice. Preferably, the first transport device is driven by a firstdrive device and the second transport device is driven by a second drivedevice. Preferably, the relative position between the reception means ofthe first drive device and the holding means of the second drive deviceis changed by controlling at least one of the two drive devices. In thisway, for example an offset between the drives can be changed.

As an alternative or in addition to the changeability of the relativeposition, the method described here it may also be provided for at leastone drive device to drive at least one transport device and for theholding elements to be moved in a longitudinal direction of the plasticpreforms by means of a further drive device. According to the invention,at least one measured value that is characteristic of the drive deviceis detected here, and the further drive device is controlled as afunction of this measured value.

Preferably, the characteristic measured value is a measured value thatis characteristic of a torque of at least one drive device for thetransport device. Preferably, this measured value is continuouslydetected and/or is compared with at least one limit value.

Preferably, as a function of this measured value, the further drivedevice can be activated and/or deactivated, i.e. for example the feedingof the holding elements towards the plastic preforms can be activatedand/or deactivated.

Preferably, the plastic preforms are contacted or guided along apredetermined region of their transport path both by the reception meansand by the holding elements. This is in particular the region in whichthe holding elements plunge into the plastic preforms. Thus, thetransfer point can also be regarded as a transfer region.

Further advantages and embodiments result from the attached drawings,wherein:

FIG. 1 shows a schematic view of an apparatus for heating plasticpreforms;

FIG. 2 shows an illustration of an apparatus for heating plasticpreforms in detail;

FIG. 3 shows an illustration of a section of the plastic preform to beheated;

FIG. 4 shows a detailed view of the first transport device;

FIG. 5 shows a view for illustrating displacements of the transfer pointin the case of different plastic preforms;

FIG. 6 shows a further view of an apparatus according to the inventionfor heating plastic preforms; and

FIG. 7 shows a further detailed view of an apparatus for heating plasticpreforms.

FIG. 1 shows a schematic view of an apparatus 1 for heating plasticpreforms 10. In the course of this, these plastic preforms 10 are fed toa first transport device 2 via a feeding device 12. This first transportdevice 2 is here a sawtooth star wheel that has a plurality of receptionmeans 22 in the form of recesses. The plastic preforms are carried inthese recesses. The first transport device 2 transfers the plasticpreforms to a second transport device 4. This second transport device 4also has a circulating transport means such as a transport chain, onwhich a plurality of holding elements 42 are arranged.

As can be seen from the figure, these holding elements also allow here arotation of the plastic preforms about the longitudinal direction or thelongitudinal axis thereof.

Reference sign 6 relates to heating devices or heating boxes used forheating the plastic preforms 10. Reference sign 29 identifies coolingdevices that apply cooling air onto the plastic preforms at least attimes during the heating thereof. In this way, an even heating can beachieved also in the radial direction of the plastic preforms. Referencesign P identifies the transport path of the plastic preforms during thetransport thereof using the second transport device 4.

FIG. 2 shows a detailed view of the device 1 for heating plasticpreforms. What can be seen again is the first transport device 2 thathas the sawtooth star wheel 24 with the reception means 22. Referencesign 25 identifies a guiding rail that guides, together with therecesses 22, the plastic preforms (not shown).

Reference sign 54 identifies a drive shaft that drives or guides adiversion wheel 52 on which a transport chain (not shown) is provided.Reference sign 112 identifies a drive device that drives, via atransmission (not shown), both the sawtooth star wheel 24 and thediversion wheel 52. In the view shown in FIG. 2, the two drives arecoupled with each other. Thus, a synchronous drive of the transport starwheel 24 and the diversion wheel 52 is provided here, as known from theprior art. Nevertheless, it would be possible here to achieve an offsetby allowing a rotational position of the transport star wheel 24relative to a drive shaft (not illustrated) to be achieved.

Reference sign 82 relates to a holder for the drive device, andreference sign 84 relates to a bottom table top.

FIG. 3 shows a detailed view of the plastic preform 10, morespecifically the upper or mouth region thereof. In this context,reference sign 10 a relates to a mouth section, reference sign 10 crelates to a carrier ring and reference sign 10 b relates to a base bodyof the plastic preform. This base body of the plastic preform has here acertain cross section L1. To this cross section, the reception means 22of the first transport device 2 are adapted. As explained above, it ispossible for the apparatus to trim and optimise itself using typeparameters. In this context, a centre offset is preferably automaticallycalculated and compensated via an angle correction. There is no need foran operator to change, convert or readjust anything mechanical. With anytype of plastic preform, an ideal adjustment of the transfer point andthus an enhanced accuracy of the preform transfer is made possible.Reference sign L identifies a longitudinal direction of the plasticpreforms.

FIG. 4 shows a schematic view of a first transport device 2 according tothe invention. Here again, the transport star wheel 24 with the recesses22 is shown. What is also shown is the outwardly circulating guidingrail 25, the position of which relative to the sawtooth star wheel 24can be adjusted. Reference sign 32 identifies a gripping element, bymeans of which the transport star wheel 24 can be removed, for examplefor mounting purposes. Apart from that, fastening means 34 are provided,which allow the transport star wheel 24 to be released. In addition, itmay also be provided that the fastening means 34 are released so as tosubsequently slightly rotate the transport star wheel 24 for adjustingan offset.

FIG. 5 illustrates the displacement of offset due to different preformgeometries. What is assumed here is a tolerance in an amount of 1 mm forthe plastic preform. In this context, a plastic preform 10 and a plasticpreform 10 a are shown, with the plastic preform 10 having a diameter of25.50 mm and the plastic preform 10 a having a diameter of 26.49 mm.Both plastic preforms are to be conveyed using the same reception means22. It can be seen that the centre point of the plastic preform isdisplaced by 0.5 mm. This in turn causes the transfer point to bedisplaced by up to 0.5 mm, so that it may deteriorate. Calculated on theradius of the sawtooth star wheel 24, this leads to an angulardisplacement from the 0.154° shown here. This angular displacement cannow be taken into consideration by the control devices of the apparatus,in order to thus correspondingly correct the transfer point.

FIG. 6 shows a view of an apparatus for heating plastic preforms. Again,the first transport device 2 and part of the second transport device 4are shown. Reference numeral 42 identifies a holding element, such ashere a mandrel, which can be introduced into the plastic preform.Reference sign 56 partially identifies a guiding cam that is used forfeeding the holding elements towards the plastic preforms. This guidingcam in particular effects an introduction of the holding mandrels 42into the plastic preforms. As mentioned above, this guiding cam canpreferably be deactivated or removed, in order to avoid damage to theapparatus, for example as a result of jamming of plastic preforms.Reference sign 50 identifies, in its entirety, the drive device that isused for moving the holding elements in the longitudinal direction ofthe plastic preforms. The guiding cam 56 is a component of this drivedevice 50.

To this end, for example an actuating device 58 (which also constitutesa component of the drive device) may be provided for moving the guidingcam, such as for example a hydraulic, pneumatic, electromotoric ormagnetic drive. By means of this actuation device, the guiding cam canbe switched off and in this way the feeding of the holding element 42towards the plastic preforms may be deactivated.

Reference sign 16 schematically identifies a control device that is usedfor controlling the drive device 50, in particular for controlling theactuating device. Reference sign 18 identifies a sensor device thatdetects a torque of the first drive device 26 and/or of the second drivedevice 46 (or a value that is characteristic thereof, such as acurrent). As a response to this detected torque, the drive device 50,more specifically in particular the actuating device 58, can be caused(in particular by means of the control device 16) to move away theguiding cam and thus to deactivate the feeding of the holding elementstowards the plastic preforms.

Reference sign U identifies a transfer point, on which the plasticpreforms are transferred from the first transport device to the secondtransport device. Correspondingly, this point could also be referred toas a take-over point, at which the second transport device 4 takes overthe transport preforms 10 from the first transport device 2. By changingthe positions of the reception means 22 relative to the holding elements42, this transfer point can be displaced.

FIG. 7 shows a further view of an apparatus according to the invention.Here, too, a first drive device 26 is shown that drives the transportstar wheel 24 via a drive shaft 27. What is also shown is a second drivedevice 46 that drives the diversion wheel 52. Reference sign 30schematically identifies a control device that controls the two drivedevices 26 and 46. In this way, the transfer point U as shown in FIG. 6can intentionally, albeit merely slightly, be displaced. Reference sign36 identifies a processor device that calculates, on the basis of thedata and in particular of the diameters of different preforms, acorrection of an offset between the two transport devices 2, 4.Moreover, input means 38 may be provided, via which the user can inputdata, for example data in relation to the plastic preform 10 to beprocessed.

The applicant reserves the right to claim all of the features disclosedin the application documents as being essential to the invention, in asfar as they are novel over the prior art either individually or incombination. It is further pointed out that the individual figures alsodescribe features which, by themselves, may be advantageous. A personskilled in the art will immediately realise that a certain featuredescribed in a figure may be advantageous, even if no further featuresfrom this figure are adopted. A person skilled in the art will furtherrealise that advantages may also result from a combination of aplurality of features shown in individual or in different figures.

LIST OF REFERENCE NUMERALS

-   L1 Cross section-   P Transport path-   L Longitudinal direction of the plastic preforms-   1 Apparatus-   2 First transport device-   4 Second transport device-   6 Heating devices/heating boxes-   10 Plastic preforms-   10 a Mouth section/plastic preform-   10 b Base body of the plastic preform-   10 c Carrier ring-   12 Feeding device-   16 Control device-   18 Sensor device-   22 Reception means/recesses-   24 Sawtooth star wheel/transport star wheel-   25 Guiding rail-   26 Drive device-   27 Drive shaft-   29 Cooling device-   30 Control device-   32 Gripping element-   34 Fastening means-   36 Processor device-   38 Input means-   42 Holding elements/holding mandrels-   46 Drive device-   50 Drive device-   52 Diversion wheel/guiding cam-   54 Drive shaft-   56 Guiding cam-   58 Actuating device-   82 Holder-   84 Bottom table top-   112 Drive device (prior art)

1. An apparatus for heating plastic preforms, comprising a firsttransport device that transports the plastic preforms in a separatedmanner, wherein said first transport device has a plurality of recessesfor receiving the plastic preforms, comprising a second transport devicethat takes over the plastic preforms transported by the first transportdevice and transports said plastic preforms along a predeterminedtransport path, wherein the second transport device has a plurality ofholding elements for holding the plastic preforms and at least oneheating device that heats the plastic preforms transported by the secondtransport device, wherein at least the first transport device is acirculating transport device, wherein the apparatus comprises a drivedevice for moving the holding elements in a longitudinal direction ofthe plastic preforms, and the apparatus has at least one drive devicefor driving at least one transport device, wherein the apparatus has atleast one sensor device that detects at least one measured value that ischaracteristic of at least one of the two drive devices, and a controldevice suitable and designed for controlling the drive device for movingthe holding elements as a function of this characteristic measuredvalue.
 2. The apparatus as claimed in claim 1, wherein the sensor devicedetects at least one measured value that is characteristic of a torqueof the at least one drive device.
 3. The apparatus as claimed in claim1, wherein the drive device has a guiding cam for moving the holdingelements, which guiding cam extends, at least in sections, along thetransport path of the holding elements.
 4. The apparatus as claimed inclaim 3, wherein the drive device has an actuation device for moving theguiding cam.
 5. The apparatus as claimed in claim 1, wherein theapparatus has a first drive device for driving the first transportdevice and a second drive device for driving the second transportdevice.
 6. The apparatus as claimed in claim 1, characterised in that atleast one drive device for driving at least one transport deviceincludes a servo motor.
 7. The apparatus as claimed in claim 1, whereina relative position of the recess of the first transport device can bechanged in the circulating direction of the first transport devicerelative to a position of the holding elements in respect of thetransport path.
 8. The apparatus as claimed in claim 1, wherein theapparatus has a processor device that determines, from at least onecharacteristic value of a plastic preform, an offset between the twodrive devices.
 9. The apparatus as claimed in claim 1, wherein saiddrive device can be deactivated for moving the holding elements duringthe on-going machine operation.
 10. A method for heating plasticpreforms, wherein the plastic preforms are transported in a recess of afirst transport device and are taken over by a second transport devicein a predetermined take-over position and are transported by said secondtransport device by holding elements that hold the plastic preformsalong a predetermined transport path, and are heated, at leasttemporally, during the transport along the transport path by at leastone heating device, wherein at least one drive device drives at leastone transport device and the holding elements are moved in thelongitudinal direction of the plastic preforms by a further drivedevice, wherein at least one measured value that is characteristic of atleast the drive device is detected and the further drive device iscontrolled as a function of this measured value.
 11. The method asclaimed in claim 10, wherein the characteristic measured value is ameasured value that is characteristic of a torque of the drive device.12. The method as claimed in claim 10, wherein the measured value iscontinuously detected and/or is compared with a reference value.